Process of obtaining permanent deposits of metals on aluminium.



NITED STATES EDUARD MIES, OF BUDESl-IEIM, GERMANY.

PROCESS OF OBTAINING PERMANENT DEPOSITS OF METALS ON ALUMINIUM.

SPECIFICATION forming part of Letters PatentNo. 647,8 58, dated April 1'7, 1900.

Application filed September 9, 1899. Serial No. 730.012. (No specimens.)

To all 107L077 it may concern Be it known that I, EDUARD MIES, a subject of the Grand Duke of Hesse,residing at Biidesheim, (Rhein-Hessen,) Germany, have invented certain new and useful Improvements in Processes for Obtaining Permanent Deposits of Metals on Aluminium; and I do hereby declare the following to be a full,clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention has for its object a process for the production of permanent deposits of metals on aluminium.

Among the processes at present known for obtaining deposits of other metals on aluminium there are none which form permanent deposits directly on aluminium. For instance, aluminium has first to be prepared in a solution of cyanid of mercury, whereby, of course, an amalgam is formed, and another metal-such, for instance, as copperis then deposited on the amalgam. This process is suitable for purposes of demonstration, but not for practical working. Metallic deposits should also ,bear a great degree of heat without losing their thorough adherence; but this is not the case with deposits made by the above-mentioned method, as it is well known that amalgams when heated lose the mercury, and the latter when heated must find some way out, whereby the metal on the amalgam is necessarily loosened.

The process proposed by Nauhardt (German Patent No. 100,786) to deposit silver directly on aluminium by means of cyanid of potassium is not a general process, but applicable only to the deposition of silver, such deposit also not being permanent, but easily peeled off.

In another process aluminium is first treated with potash lye, the said lye not being washed off, and then the metallic deposition is effected thereon. The drawbacks of such a process appear from the following:

If metallic aluminium be dipped in a 1yefor instance, potash lye-there is formed aluminate of potash or aluminous oxid of potassium, according to the formula Al GKOH A] (OK) 3H,, hydrogen being given off. It is thus impossible to produce a permanent deposit on metallic aluminium, since the lye is not removed or washed off, and the whole surface of the metal is therefore coated with aluminous oxid of potassium, which on being melted by heat and in view of its tendencyto vaporize results under greater expansion in a deposit which does not firmly adhere to thealuminium, but is more properlya loose deposit. If it be further considered that potash lye is also mechanically retained by the aluminous oxid of potassium, there must also take place afurther evolution of gas, as the aluminous oXid of potassium is not washed off, which evolution of gas prevents .a firm adherence of the deposit on the aluminium- Even if in many cases a firm connection of the deposited metal on the aluminium appears at firstthat is to say immediately after the deposit is formedto be solidly established, yet after a certain timethe coating always becomes loosened when formed by the methods hereinbefore described.

The process which forms the object of the present invention removes these drawbacks and is entirely different from the processes hereinbefore mentioned.

In this improved process the metallic aluminium in the form of sheets, wire, or the like is heated for about five minutes in a boiling solution of phosphate of sodium and sulfate of magnesium, slightly acidulated with sulfuric acid, then washed with water and subjected to the action of the electric current in the ordinary baths of metallic salts, such as copper, zinc, tin, or the like.

By boiling with the above-described salts the surface of the aluminium'appears to be corroded in such a manner as to become rough, although this is hardly sensible or visible, whereby and by washing off the acting solution the metal deposited on the aluminium adheres firmly thereto and forms an inseparable coating therefor.

By this improved process numerous depositions in baths of copper, zinc, tin, and the like have been obtained, which are all characterized by the inseparability of the deposits from the aluminium. No after evolution of gas and no scalingoff when heated is here possible, and all the known disadvantages of otherprocesses are avoided.

In place of phosphate of sodium sulfuric and any other compound Which attacks alu- .phate of a metal, a free acid-and a compound capable of attacking aluminium in thepresence of said acid, then washing the aluminiminium' in a solution of a mixture of aphos- E. SOI-IUMANN.

um and effecting the deposition 'electrolytic- 2 5 5 minium in the presence of such a free acid ally in a solution of the salt of the metal to may be employedas, for instance, phos-. be deposited, substantially as set forth. phoric acid or acetic acid or sodium chlorid 2. The process of depositing'metals on aluand phosphoric metal compounds-such as minium, which consists in boiling the aluphosphate of potassium, magnesium, or aluminium in an acidulated solution of a phoso 10 minium. i a l phate of a metal and of sulfate of magnesium,-

I The function of the sodium phosphate in then Washing the aluminiumand effecting combination with magnesium sulfate is not the deposition electrolytically in a solution known definitely; but-it is believed to have a of a salt of the metal to be deposited, subcertain etching eifect on the aluminium surstantially as set forth. 3 5

I5 face. g or In testimony Wnereot I affix my signature c Having thus described my invention, What in presence of two Witnesses.

Iclaim as new therein, and desire to secure by Letters Patent, is V EDUARD MIES' 1. The process of depositing metals on alu- Witnesses: 2o 'minium, which consists in boiling the alu- S. LAREY, 

